The MB_PRO connector is used to connect a Sound Blaster card to a Modem Blaster card. The signals can also be re-purposed for other uses.
The pin arrangement is as follows:
The purpose of the pins, from the point of view of the sound card, are:
|2||Key, no pin|
|5||Line left TODO: Is this line out?|
|7||Line right (out?)|
|8||Modem speaker input. On a sound card, this input receives a line-level audio signal from the modem.|
|10||Microphone in Isn't this mic out for the modem?|
Some sound cards have an MB_PRO connector but no TAD connector. A cable can be made to allow internal modems with a TAD socket to be hooked up to the MB_PRO connector:
| Sound card
|1||8||Phone line audio, from modem to sound card.|
|4||10||Microphone audio, from sound card to modem.|
TAD pins 2 and 3 can also be patched to any of the other GND signals on the MB_PRO connector if that is more convenient. The two in the above table are just one possibility.